Jet exhauster



June 27, 1961 H. COANDA ETAL 2,990,103

JET Em-IAUSTER Filed Sept. 1, 1959 5 Sheets-Sheet 1 FIGJ June 27, 1961Filed Sept. 1, 1959 H. COANDA ETAL JET EXHAUSTER I I 10 9 5 3 dz 5Sheets-Sheet 2 June 27, 1961 H. COANDA ETAL 2,990,103

JET EM-IAUSTER Filed Sept. 1, 1959 s Sheets-Sheet 3 FIG.3

53 \l {1 24/ 30 31 L 2 25. 4 if 33 June 27, 1961 H. COANDA E'AL2,990,103

JET EXHAUSTER Filed Sept. 1, 1959 5 Sheets-Sheet 4 June 27, 1961 H.COANDA ETAL 2,990,103

JET EXHAUSTER Filed Sept. 1, 1959 5 Sheets-Sheet 5 FIGS United StatesPatent 2,990,103 JET EXHAUSTER Henri Coanda, Paris, MargueriteRibeyrolles, nee Gantillon, Clichy, and Michel Garnier, Paris, France,as-

signors to Sebac Nouvelle S.A., a corporation of Switzerland Filed Sept.1, 1959, Ser. No. 837,409 Claims priority, application France Sept. 8,1958 5 Claims. (Cl. 23095) The present invention relates to an exhausterdevice for creating one or a number of zones of reduced pressure orpartial vacuum by means of the flow of a flat fluid jet.

When a flat jet of fluid (gaseous or liquid) passes out of an orifice ofrectangular section, which may be limited by walls or may be continuous,and passes into another fluid, and when a body is brought up to one ofthe larger sides of the rectangle which forms the jet, under certainconditions, surprising eifects are obtained.

The first surprising effect consists in that, when the body which isbrought up is connected to the chamber from which the jet issues, sothat it creates a space isolated from the ambient fluid into which thejet discharges, it is found that on all sides except on the side of thejet, in the case of air under a certain pressure, when the angle abetween the direction of the jet and the straight line drawn from theedge of the outlet orifice and passing tangentially to the bodyapproaches 32, there is created in the space a very high pressure dropor partial vacuum which has the unexpected characteristic of beingattenuated when the angle a diminishes. This is true While the samepressure on the upstream side of the jet, the same outlet section andthe same distance of the body from the outlet of the jet are maintained.

Still a more surprising efiect is that which is produced in the jetitself, which is first of all turned or curved inwardly towards thebody, accelerates its speed of flow and reduces its internal tension toa value substantially below the pressure obtaining in the ambient fluid.This has as its first result that the mass of the jet flowing throughthe same outlet section with a given upstream pressure is increased andsecondly, the ambient fluid rushes into the zone of reduced pressurecreated in the jet, and re-establishes its pressure Without reducing thespeed of flow to any considerable extent, which has the result ofsubstantially increasing the momentum per second of the jet.

As soon as the jet reaches the body, if another body is brought close tothe jet it thus turned inwardly, and if the same conditions areobserved, the phenomenon repeats itself and a new zone of reducedpressure is created between the first body and the second, and thissecond zone is smaller than the first, with the result that the speed isslightly reduced, but the jet continues to increase its mass by theambient fluid which has flowed in to fill the new reduced pressure zonecreated in the jet. The stages of this flow can be continued in this wayso as to obtain several stages of reduced pressure zones, while themomentum is continually increased.

The applications for an arrangement of this kind are very numerous. Forexample, as has been stated above, a large momentum can be producedwithout increasing the upstream pressure of the jet. Also, the spacescan be connected to chambers in which it is desired to maintain areduced pressure. Further, it is possible to make use of these pressuredrops for all kinds of other applications, such as the suction of liquidinto the jet in order to produce a spray. The pressure drop or reducedpressure zones so created can also be employed to produce a lift eifectby adapting it to an aircraft wing, etc. The characteristic feature ofthe present invention resides in the method which consists in the use ofa flat 2,990,103 Patented June 27, 1961 fluid jet to create one or morereduced pressure zones by bringing up to one of the longer Sides of theflat jet, of limited or continuous rectangular section, one or a numberof bodies of appropriate shape. The first body is located at apre-determined position with respect to the outlet orifice of the jetsuch that, for example in case of air, the angle between the directionof the jet and a straight line drawn from the orifice and passingtangentially to the first body is less than 32, and such that thedistance between the body and the orifice is less than twelve times theheight of the jet and the ratio between the pressure on the upstreamside of the jet and the ambient fluid is less than thirty. The secondbody of appropriate shape should be located in such manner with respectto the first body that the straight line drawn from the extreme point ofthe first body and passing tangentially to the second body forms anangle less than 30 with the extension of the tangent which starts fromthe outlet orifice to the first body, the distance being less thantwelve times the thickness of the jet opposite the first body, and soon.

The characteristic values given above correspond to air, and varyaccording to the fluid considered.

The determination of the value of the reduced pressure zones is effectedeither by reducing the dimensions of the angles on, or by acting on thepressure on the upstream side of the jet, or by acting on the ratiobetween the distances existing between the element carrying the jet andthe bodies, and also by acting on the height of the jet. Thisdetermination can be made either by each of the above means takenseparately, or by employing any combination of these means.

Several forms of construction of devices according to the invention aredescribed below by way of simple example, reference being made to theaccompanying drawings, in which:

FIG. 1 is a front view of a first device according to the inventionhaving a limited rectangular section;

FIG. 2 is a cross-section taken along the line 11-11 of FIG. 1;

FIG. 3 is a cross-section of a hollow discharge nozzle device providedwith bodies of revolution;

FIG. 4 is a fragmentary view of the same device on an enlarged scale;and

FIG. 5 is a cross-section of an alternative form, in which the dischargenozzle, provided with bodies of revolution, discharges towards theexterior.

The device shown in FIGS. 1 and 2 comprises a member 1 in which isformed a chamber 2 having an outlet onifice formed by a slot 3 ofrectangular section. The slot is limited at its two extremities by walls4 to which the member 1 is attached and which prevent ambient fluid fromacting at the sides of a gaseous jet 5 discharged under pressure fromthe chamber 2 through the slot 3. The walls 4 form and define an intakefor an ambient fluid to be moved by the gaseous fluid under pressuredischarged from the chamber 2 as a jet.

A body 6, attached by a support 7 to the member 1 and the walls 4,creates a space 8 which is isolated fr the ambient fluid.

When the angle at existing between a plane 9 corresponding to thedirection of the outlet of the jet 5 and a straight line which connectsa portion 10 of the slot 3 to the body 6, to which it is tangential at asurface 11, is less than 32, the jet 5 can be seen to curve inwardly andpass in contact with the surface 11 of the body 6, while a substantialpressure drop is observed in the space 8.

After having passed over the surf-ace 11 of the body 6, the jet againcurves inwardly through an angle a less than 25, towards a second body12 which is attached like the body 6 by a support 13 to the member 1 andto the walls 4. In the space 14 created by the second body 12, apressure drop is also produced. The jet which has been deflected fromthe surface 11 of the body 6, now passes over a surface 15 of the body12, after which. it is again curved through an angle m less than 20 andis then directed towards a surface 16 drawn by the action of a thirdbody 17, while creating a new space 18 in which a pressure drop is alsoproduced.

Finally, the jet passes along a surface 19 and leaves the surface of thebody 17, with which is makes an angle a which is less than 15 In theabove device, the value of the reduced pressures in the spaces 8, 14 and18 can be reduced by reducing the heights h, h and h of the spacesrespectively.

In the device shown in FIGS. 3 and 4, the operation is similar to thatof the device shown in FIGS. 1 and 2, but there are no longer anylateral walls and the slot is continuous.

In this device, a gas under pressure enters through a pipe 20 and isdistributed in a circular chamber 21 from which it issues as a jetthrough a circular slot 3.

The circular chamber 21 is formed above a cylindrical body 22, in whichare mounted, one above the other, a plurality of annular bodies 23, 24,25 and 26 which act on the jet.

The air passing out of the slot 3' is drawn towards the first annularbody 23 and passes over a surface 23a, thus producing a very highpressure drop in the annular space 27. The jet of air is accelerated andits internal tension is less than that which obtains in ambient airdenoted by the arrows 28. This air rushes into the jet and the wholemixture is then drawn towards the second annular body 24 and produces areduced pressure in the annular space 29.

Having passed over a surface 30 of the body 24, the jet is again curvedinwardly by the pull of the body 25, creating a reduced pressure zone ina space 31. After passing over a surface '32 of the body 25 and asurface 33 of the body 26, the mixture of the jet and the ambient air 28which it has carried along, reaches the level of a throat 34. At thispoint, under the drawing-in action of the wall 35, it creates at 36 alast reduced pressure zone which imparts a final acceleration to themixture.

Subsequently, in accordance with Bernouillis law, the mixture of the airof the jet and the ambient air slows down its movement in the divergentsection 37 and transforms its kinetic energy topotential energy up to anoutlet zone 38, where it leaves the entire device, which in this caseacts as an ejector-injector at 39.

In the embodiment shown in FIG. 5, the bodies which define the spaces orzones in which a reducedpressure is created and aifect the form andcourse of the jet constitute a single block of revolution 40 external toand fitting over a central tubular member 41.

A cap 42 forms an annular chamber 43 with the tubular member 41. Thischamber opens into the ambient, fluid denotedby the arrow 45, through acircular slot 44.

The fluid under pressure, illustrated by the arrow '5, passes out of theslot 44 and the jet is subjected to the successive attractions of theprojections 46, 47 and '48 formed at'the periphery of the outer block 40and defining spaces 49, 50 and 51 in which a reduced pressure iscreated.

The operation of this device is the same as in the devices previouslydescribed.

The devices described above have been assumed to be traversed by air,but it is clear that the invention can just as well be applied to allother devices intended for all otherdiquid or'gaseous fluids, bymodifying the dimensions and characteristics of some of their members.

If, for example, itis desired to apply thedevices-to a fluid which isheavier than air, for example water, the reasoning which has enabled thevalues "for airto be .4 determined in the examples previously described,should be completed as follows:

It is considered that the adhesion of a fluid stream to a predeterminedpoint is due to an imbalance produced between the ambient pressure,acting on one side of the flat jet, and the vacuum produced on theopposite side of the jet.

On the other hand, the detachment of the jetiscansed by centrifugalforce applied to the jet and which, for the above reason, prevents thecavity in which the reduced pressure is created from being madefluid-tight at a certain moment.

This centrifugal force is equal to in which m is the fluid mass, V isits speed at the moment when the jet touches the desired point, and r isthe radius of curvature, the arc of which represents the line whichmakes an angle with the original direction of the jet.

The speed due to an isentropic flow for air is given by:

V=44.81S /T T or again by the equation of condition:

PW=RgT, P W =RgT and we have PW P W P Rg dR Rg d R in which W is thevolume, P the pressure, g the weight, d the density and R the constantof the gases.

In the case of air, the speed of flow can therefore be Written asfollows:

T etc.

V,,=44.8l8 E In the case of water, the speed of flow is:

V /2gH and therefore r o V, 44.4 (2) since in the case of water,

from (1) and (2) it may be deduced that the ratio between the speed orair and the speed of water for the same pressures, will be approximatelyas follows, to within 1% Assuming that P =10,000 (which is not quiteaccurate, since in the case of water we are about one meter below thelevel) the above can give in round figures an order of magnitude, forinfrasonic speeds of air especially:

1 2:100 a R r 1 o) S and 8, being the crosssection-of the-jets ofair andof Watenrespectively,

1 1.5 a a e Z1230 P1-Po 1,: a a e a from which can be found the value ofthe are, its length, etc. for the same vacuum createdon one side of thejet.

It can therefore be seen that by a simple calculation it is possible todetermine the angles and therefore the shapes.

It should also be observed that in view of the partial vacuum createdbehind the jet of water, there will be produced in this reduced pressurezone an evaporation of the water which will partly fill this zone. a

What we claim is: a

1. A device for creating at least one reduced pressure zone by the flowof a substantially flat fluid jet comprising, means defining a chambersupplied with fluid under pressure and having two spaced, elongated lipsdefining a nan-ow elongated slot of continuous uniform substantiallyrectangular section formed communicating with said chamber fordischarging a flat jet of said pressure fluid therefrom in a giveninitial direction, means defining a wall fast with said means definingsaid chamber and extending perpendicularly to a plane disposed in adirection corresponding to the longitudinal dimension of said slot andcorresponding to an exit axis of said slot which corresponds to theinitial direction of fluid flow through said slot, a first membermounted on said wall extending therefrom and spaced axially from and inclose relation to the nearer of said lips defining said slot and havinga sloping outermost face spaced from said wall to deflect the jet fromits direction of flow and forming in conjunction with said jet and thewall a fluid-tight space, said first member sloping face being so formedand axially spaced from said slot that an angle included between saidplane corresponding with the initial direction of flow of the jet and astraight line tangential to the outermost tip of said nearer lip of saidslot and passing tangentially to said outermost sloping face on saidfirst member has a predetermined value dependent on the nature of saidfluid, and a plurality of other members mounted axially Spaced on saidwall extending therefrom and axially spaced from said first member, andeach of said other members being formed with an outermost sloped facespaced axially from the outer sloped face of a preceding member which isdisposed in a direction toward said slot relative to a next succeedingother member so that respective angles included between intersectingstraight lines each disposed tangentially to the outermost tip of thesloped face of a preceding member and disposed tangentially to the outersloping face of the next succeeding member progressively diminish invalue relative to each other, and means on said device forming anddefining an intake for ambient fluid and directing it in a downstreamdirection toward said elongated slot to be moved by said jet of fluidunder pressure, said intake defining means being disposed on said deviceupstream of said slot.

2. A device for creating at least one reduced pressure Zone by the flowof a substantially flat fluid jet comprising, means defining a chambersupplied with fluid under pressure and having two spaced, elongated lipsdefining a narrow elongated slot of continuous uniform substantiallyrectangular section formed communicating with said chamber fordischarging a fiat jet of said pressure fluid therefrom in a giveninitial direction, means defining a wall fast with said means definingsaid chamber and extending perpendicularly to a plane disposed in adirection corresponding to the longitudinal dimension of said slot andcorresponding to an exit axis of said slot which corresponds to theinitial direction of fluid flow through said slot, a first membermounted on said wall extending therefrom and spaced axially from and inclose relation to the nearer of said lips defining said slot and havinga sloping'butrmost face spaced from said wall to deflect the jet fromits direction of flow and forming in conjunction with said jet and thewall a fluid-tight space, said first member sloping face being so formedand axially spaced from said slot that an angle included between saidplane corresponding with the initial direction of flow of the jet and astraight line tangential to the outermost tip of said nearer lip of saidslot and passing tangentially to said outermost sloping face on saidfirst member has a predetermined value dependent on the nature of saidfluid, and a plurality of other members mounted axially spaced on saidwall extending therefrom and axially spaced from said first member, andeach of said other members being formed with an outermost sloped facespaced axially in a'direction toward said slot relative to a nextsucceeding other member so that respective angles included betweenintersecting straight lines disposed tangentially to the outermost tipof the sloped face of a preceding member and disposed tangentially tothe outer sloping face of the next succeeding member progressivelydiminish in value relative to each other, and said means defining saidchamber forming and defining an intake for an ambient fluid to be movedby said fluid under pressure.

3.'A device as claimed in claim 2, in which said fluid under pressure isair, the angle included between the first-mentioned plane and the planedisposed tangentially to said first member sloped face has a value lessthan 32, the distance between the first member and said nearer lip beingless than twelve times a thickness dimension of the jet in the vicinityof said slot, and the ratio of the fluid under pressure at said slot tothe pressure of the ambient fluid is less than 30.

4. A device for creating at least one reduced pressure zone by the flowof a substantially flat fluid jet comprising, means defining a chambersupplied with fluid under pressure and having two spaced, circular lipsdefining a narrow, circular slot of continuous uniform substantiallyrectangular section formed communicating with said chamber fordischarging a flat jet of said pressure fluid therefrom in a giveninitial direction, circular means defining a wall fast with said meansdefining said chamber and extending perpendicularly to a plane disposedin a direction corresponding to the length of said slot andcorresponding to an exit axis of said slot which corresponds to theinitial direction of fluid flow through said slot, a first membermounted on said wall extending therefrom and spaced axially from and inclose relation to the nearer of said lips defining said slot and havinga sloping outermost face spaced from said Wall to deflect the jet fromits direction of flow and forming in conjunction with said jet and thewall a fluid-tight space, said first member sloping face being so formedand axially spaced from said slot that an angle included between saidplane corresponding with the initial direction of flow of the jet and astraight line tangential to the outermost tip of said nearer lip of saidslot and passing tangentially to said outermost sloping face on saidfirst member has a predetermined value dependent on the nature of saidfluid, and a plurality of other members mounted axially spaced on saidwall extending therefrom and axially spaced from said first member, andeach of said other members being formed with an outermost sloped facespaced axially from the outer sloped face of a preceding member which isdisposed in a direction toward said slot relative to a next succeedingother member so that respective angles included between intersectingstraight lines disposed tangentially to the outermost tip of the slopedface of a preceding member and disposed tangentially to the outersloping face of the next succeeding member progressively diminish'invalue relative to each other, and said means defining said chamber beingannular in shape forming and defining an intake for an'ambient fluid tobejmoved by said fluid under pressure.

5. A device for creating at least one reduced pressure zone by the flowof a substantially flatfluid jet comprising, means defining a'charnbersupplied withfluidiunder pressure and having two spaced lips defining anarrow slot of continuous uniform substantiallyr'ectangular sectionformed communicating with said 'charnberfor discharging a-fiat jet'ofsaid pressure fluid therefrom in a given initialdirection, meansdefining a wall fast with said means defining said chamber and extendingperpendicularly to a plane disposed in a direction corresponding to thelongitudinal dimension of said slot and corresponding to an exit axis ofsaid slot which corresponds to the initial direction of fluid flowthrough said slot, a first member mounted on said wall extendingtherefrom and spaced axially from and in close relation to the nearer ofsaid lips defining said slot and having a sloping outermost face spacedfrom said wall to'deflect the 'jet from its direction of flow andforming in conjunction with said jet and the wall a fluid-tight space,said first member sloping face being so formed :and axially spaced fromsaid slot that an angle'included between said plane corresponding withthe initial direction of flow of the jet and a straight line tangentialto the outermost tip of said'nearer lip of said slot and passingtangentially to said outermost sloping face on said first member has apredetermined value dependent on the nature of said fluid, and aplurality of other members mounted axially spaced on said wall extendingtherefrom and axially spaced from said first member, and each of saidother members being formed with an outermost sloped face spaced axiallyfrom the outer sloped face of a preceding member which is disposed in adirection toward said slot relative to a next succeeding other member sothat respective angles included between intersecting straight lines eachdisposed tangentially to the outermost tip of the sloped face of apreceding member and disposed tangentially to the outer sloping face ofthe next succeeding member progressively diminish in value relative toeach other and means on said device forming and defining an intake forambient fluid and directing it in a downstream direction toward saidelongated slot to be moved by said jet of fluid under pressure, saidintake defining means being disposed on said device upstream of saidslot.

No references cited.

